reversal processing of Black&White paper
For fun I've been trying to reverse process black and white paper. This would mean putting enlarging paper in the camera, expose, and process to get a positive image.
The process seems simple, and is similar to reversal processing of black and white film- develop, bleach, clear, re-expose to white light, develop, then fix.
I got the process details from an old RIT paper. Here's the process (I assume it uses RC paper):
1st developer 30-60 sec
rinse 30 sec
bleach R-9 30-60 sec
rinse 30 seconds
Clear CB-1 30 seconds
Rinse 30 sec
Expose to light (40 watt bulb for 5-10 sec at 12 inches)
fix as usual
R-9 is 9.5 g Potassium Dichromate + 66g Sodium Bisulfate into 1L
CB-1 is 90g Sodium Sulfite into 1L
I follow the directions and get an almost solid black print! I know the initial exposure is close to correct because I can see the negative image come up in the first developer tray.
It is as though the print never got bleached, though I could see the bleach work in the tray. I tried lengthening the time in the bleach, then reducing the time in the bleach. Still all black. I tired varying the amount of time of the re-exposure to white light, still all black.
When I say almost black, I mean it is all black except for a few spots that were specular highlights in the scene.
Can anyone clue me into what I might be doing wrong? Or what I could try?
According to the text, if I had some sodium sulfide I could skip the re-exposure to white light and use Sulfide Redeveloper T-19.
keitho at strucktower dot com
Actually, there are two possible solutions that come to mind.
The paper is probably too slow (not fast), and needs a LOT more exposure, or the first development time is too short and does not develop all of the silver. A third possible answer may lie in the fact than many reversal first developers require a silver halide solvent to kick them off. This latter thought may be way off, and people differ on the effectiveness of solvents on reversal processing like this.
In every case I have tried it, I have had to use about 2 - 4 stops more exposure than appear to be needed to get a good negative image. You will probably get very high contrast and may have to use a grade zero paper for a good print.
Last edited by Photo Engineer; 12-11-2008 at 09:55 PM. Click to view previous post history.
Reason: Spelling as usual. :(
WAG or an actual photographic engineer. You be the "decider"
Is your bleach rehalideifying (can never remember that word) the silver? Either that or you need more original exposure like PE said, although I would assume that if you saw an image at first SOMETHING would appear in the final print.
Just turn on the lights. There's no need to be super-scientific about it.
The bleach must have NO halide in it or you will get no image at all. It must be a dichromate-sulfuric acid bleach or a permanganate bleach. The word is "rehal" bleach. You must not use one in this type of situation.
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You may need to give a flash exposure after the image exposure to reduce the density. Remember there is more silver than is needed to make a photograph. You have to remove the this extra silver by first development and then bleaching it away just like you are doing to the negative image first obtained with the camera.
Originally Posted by keithostertag
Are you using variable contrast paper? If so I would expect black as there would be some under exposed silver. The bleach removed the exposed silver, but there would still be unexposed silver.
Try graded paper or simpler, freestyle has direct reversal paper and develop as normal.
Thanks for your responses. I forgot to say that the instructions say to use a high contrast developer, but then goes on to say that Dektol 1:1 would "probably" work. Well, I fugured that if Dektol would work then my LPD would work... my mistake. I will try a high contrast dev and if that doesn't work I will try adding some hypo. I will post the results in a day or so. Keith.
keitho at strucktower dot com
Keith, there's a thread about the old style B&W photo-booths here somewhere the use Reversal processed paper.
Note the formulae are only whats stated on the MSDS's or somewhere showing the main ingredients.
I suspect you are using too weak a developer and also under developing, as well as maybe exposure issues. Most First developers for reversal processing are quite contrasty and development is total, that means all exposed silver halide is developed. You can get a good idea of the papers camera speed by making Paper negatives using the same developer, then move on to reversal processing and fine tune the speed. As a rule of thumb a print developer is usually used at up to twice the normal strength for reversal processing of film so for example 1+4 instead of 1+9
Back in the early 70's I saw some superb B&W prints made by the reversal process, so I know it's capable of great things.
Pe; back when R printing was around I was considering modifying the process to accept B&W RC paper [light reversal]. do you think a modification of the R process would be a better reversal B&W printing solution?
Originally Posted by Photo Engineer